A number of pressure core barrels adapted to take and seal core samples therein to the surface for disconnection and attachment to flushing apparatus prior to freezing removal and analysis of the core sample are disclosed in U.S. Pat. Nos. 2,238,609; 2,287,909; 2,381,845; 2,412,915; 2,445,494; 2,734,719; and 3,548,958.
Another improved pressure core barrel of the type disclosed in U.S. Pat. No. 3,548,958 and an improved above hole flushing system therefor is disclosed in a pending application Ser. No. 99670 now U.S. Patent No. 4,272,987 assigned to the assignee of record in the instant invention.
However, the applicant is unaware of any prior art methods or apparatus for flushing a core barrel situated downhole at existing downhole conditions and pressure prior to sealing the core sample taken therein and its removal to the surface for disconnection, freezing, removal and analysis.
The applicant's invention is unique in that it allows the flushing and displacement of drilling fluid and mud from any core barrel and particularly a pressure core barrel to be accomplished in situ or at bottom hole conditions. This also precludes the loss of bottom hole pressure from the core sample currently encountered when the flushing operation is carried out at the surface.
Further advantages are that the viscous flushing medium will enhance removal of solids from the pressure core barrel and thereby increase the reliability and more successful sealing valve closure thereof.
Less handling is required at the surface which reduces the possibility of pressure loss and the time between core sample recovery and the forwarding thereof for analysis.